The ability to accurately detect the developing lesions at early stage in dental practice and to quantify the lesions will provide dentists with the opportunity of initiating early prophylactic treatment; correct diagnosis of a fractured tooth in is earliest possible stage encourages more conservative treatment options as well as an improved prognosis. We propose a tri-modal imaging technique integrating polarized reflectance, fluorescence, and with the near-infrared (NIR) transillumination imaging modalities for early caries detection and tooth crack detection. Each imaging modality is based on distinct contrast mechanism and correlates with each other and/or complements each other in detecting caries, stain, calculus, and other property changes of tooth structure. Therefore, the tri-modal imaging technique will be more sensitive to tooth decay and will provide higher specificity in detecting demineralized tooth regions with the complementary information from each modality. With polarized NIR reflectance imaging and NIR transillumination imaging, the tri-modal imaging technique will be more sensitive in detecting tooth crack because the polarized reflectance imaging collects the scattered light inside the tooth and the transillumination imaging detects the local variation in light scattering and transillumination. In addition to individual reflectance imge, fluorescence image, and transillumination image, we will investigate the contrast enhancement of caries lesion with fluorescence ratio imaging and ratio imaging between the fluorescence image and polarized reflectance image. We will also investigate the optimal NIR wavelength for polarized reflectance imaging and transillumination imaging in tooth crack detection. We will demonstrate the proposal concept of tri-modal intra-oral camera and verify its performance in detection of caries and tooth crack. The result of this Phase I project is the tri-modal imaging technique for caries and crack detection and the concept of a low cost and compact intra-oral camera which will be implemented in Phase II for pre-clinical study. One of the core-strengths of this project is the strong interdisciplinary research team. It brings together the researcher in system development, detection electronics, and produce commercialization (Dr. Zhou), the research in developing intra-oral camera and optical technologies (Dr. Liang) and the expert in Cardiology and in evaluating various optical technologies in detection, diagnosis and management of caries (Dr. Amaechi).